Electric vehicles utilizing an electric motor as a power source and hybrid vehicles utilizing a combination of an electric motor as a power source with another power source (e.g., an internal combustion engine or a fuel cell) have become commercially available. These vehicles are equipped with a power storage device for supplying electric power as energy to the electric motor. The power storage device includes power storage equipment such as a secondary battery, a capacitor or the like that can be charged and discharged repeatedly. The secondary battery is implemented by a fuel cell such as a nickel-cadmium battery, a nickel-hydrogen battery or a lithium ion battery.
Some power storage devices include a single power storage cell, while others include a power storage module in which a plurality of power storage cells are fixed integrally. In a power storage device, a power storage module is housed in a case, for example. Since the power storage module includes a plurality of power storage cells, a large current and a high voltage can be obtained (cf. Japanese Patent Laying-Open No. 2006-156392, Japanese Patent Laying-Open No. 2005-116429 or Japanese Patent Laying-Open No. 2004-139924).